Rotatable piezoelectric tuning device



Jan; 1%? R. HILTON ETAL ROTATABLE PIEZOELECTRIC TUNING DEVICE Filed July 24, 1963 United States Patent 3,300,665 ROTATABLE PIEZOELECTRIC TUNING DEVICE Roy Hilton and Frederick George Powles, London, England, assignors to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Filed July 24, 1963, Ser. No. 297,336 Claims priority, application Great Britain, Aug. 10, 1962, 30,795/ 62 Claims. (Cl. 310-91) This invention relates to radio equipment having a plurality of switched tuning elements, and to methods of assembly of the tuning elements.

According to the present invention there is provided radio equipment having a plurality of switched circuit elements wherein the. elements are contained within a rotatable tuning knob.

Radio equipments made according to the invention occupy less space than previous similar equipments, and therefore have particular advantage for mobile use, for example in aircraft, where space is at a premium.

An embodiment of the invention will now be described with reference to the accompanying drawings of which:

FIG. 1 shows a side elevation of a crystal turret assembly,

FIG. 2 shows a cross section through the assembly of FIG. 1 on the line A-A, and a cross section of the tuning knob, the fixed contacts and the equipment panel in the inventive relationship with the assembly of FIG. 1,

FIG. 3 shows a front end elevation of the assembly of FIG. 1,

FIG. 4 shows a rear end elevation of the assembly of FIG. 1.

Referring to FIGS. 1 and 2, a strip 1 of polyvinyl chloride is formed into a circular ring which is clamped between two circular end cheeks 2 and 3, made from a thermoplastic material and mounted on a metal boss 4, the strip 1 being located in circular grooves 5 in the end checks 2 and 3. The end cheek 2 is flanged at 6 and forms an interference fit with a flanged metal plate 7. Three studs 8 are silver soldered into plate 7 and the end cheek 2 is clamped between the plate 7 and the boss 4 by three ring nuts 9 which are screwed on to the studs 8 and are located within holes 25 counter-bored in the boss 4.

The end cheek 3 is retained in position by a spring clip 10 which is inserted in a circular depression 24 (FIG. 4) counter-bored into its outer face and located in a groove 23 in the stem of the boss 4. The spring clip 10 is slightly bowed along its longitudinal axis and presses the end cheek 3 against the strip 1. In order to prevent any rotation between the strip 1 and the end checks 2 and 3, the strip 1 is locked to the end cheeks by means of pins (not shown).

Twenty crystals in tapered metal cans 11 are mounted on the circumference of the circular strip 1. In FIG. 4 a part of the end check 3 has been cut away to show the arrangement of the crystals on the strip. When all the crystals are in situ they are arranged almost touching one another in order to minimize the space occupied.

Each of the crystals is fitted with two domed silver contacts 12 which project through holes drilled on the strip 1. The crystal cans 11 are held in position by a ring of plastic foam 13 which is glued around a brass cylinder 14 which fits loosely on the stern of the boss 4. The plastic foam is sufficiently resilient to take up tolerances in the height of the cans 11. The cylinder 14 is used because it has been found that if the ring of plastic foam 13 is glued directly to the boss 4, rotation of the crystal turret tends to puta strain on the crystal cans. The boss 4 is mounted on a D-shaped tuning control shaft 20 extending through equipment panel 26. FIG. 2 illustrates shaft 20 extending through panel 26 engaged in boss 4, broken along its length to provide a clear illustration of clip 10.

The stem of the boss 4 forms a tube the bore of which is D-shaped as shown at 15 (FIG. 3). The boss 4 is locked in position on the D-shaped portion of tuning control shaft 20 by two grub screws located in the two tapped holes shown at 16 (FIG. 3). Before attaching the tuning knob 27 to the boss 4, an annular strip 28 upon which a frequency scale is engraved is fitted around a stepped portion 18 of the boss 4, and is held in position by the tuning knob 27. The front face of the tuning knob 27 includes an annular transparent portion 29 so that the frequency scale may be seen. The skirt 30 of the knob 27 is deep enough to enclose the whole of the turret assembly.

The strip 1 is pro-formed into a circular shape by a hot tool. The circular strip is then supported on a ring and the twenty pairs of holes which take the crystal contacts 12 are drilled in the strip by using a drilling jig in the form of a drilled cylinder within which the strip 1 is inserted.

The circular strip 1 is sufficiently flexible to allow it to be strained open while the crystals housed in the cans 11 are mounted on the inner circumference of the ring formed by the strip 1. The use of a strip of resilient material which can be strained open while the crystals are assembled on the strip is an important feature of the embodiment of the invention. If the strip were .preformed into a circular ring which could not be opened out, it would be difficult to assemble the last few crystals on the strip owing to the very small clearance between them. In addition, due to the tendency of the strip to contract into circular form, the crystals tend to be selfretaining during this part of the assembly.

When the twenty crystals have been assembled the strip is released to fit in the circular grooves 5 in the end cheeks 2 and 3. A gap of about /6 inch, shown at 31 (FIG. 1), is left between the ends of the strip 1 when released.

The longitudinal position of the crystal turret assembly is adjusted on the tuning control shaft 20 so that the spring contacts 19 engage with the dome crystal contacts 12. Contacts 19 being disposed in a fixed position by being fastened to panel 26 in aperture 32 by insulation 33.

The boss 4 is then locked to the tuning control shaft 20 by tightening the grub screws located within the holes 16 (FIG. 3).

The tuning control shaft 20 is coupled by means of gearing to other parts of the tuning arrangements of the transmitter/receiver. It is therefore necessary to ensure that the correct relationship exists between the frequency of each crystal selected and the angular setting of the tuning control shaft 20. This is achieved by arranging the crystals on the strip 1 in order of frequency, and during the assembly of the crystal turret the tuning control shaft 20 is set to the maximum or minimum frequency setting, and the ring nuts 9 are slackened to allow the crystals to be rotated relative to the tuning shaft 20 until the correct pair of crystal contacts engage centrally with the spring contacts 19. The ring nuts 9 are then tightened clamping the end cheek 2 to the boss 4.

The frequency scale 28 is then fitted on to the stepped portion 18 of the boss 4 and is adjusted so that the frequency indicated bears the right relationship to the crystals in the turret, which are arranged in order of frequency. Finally, the tuning knob 27 is attached to the boss 4 by counter-sunk screws 34 being threaded into the tapped holes 17.

Although th use of crystal tapered cans greatly reduces the size of the crystal turret, crystals housed in cans which are not tapered may be used if the additional volume occupied by the assembly can be tolerated. The crystals could be mounted on the convex surface of the strip 1, instead of on the concave suface, but this would greatly increase the volume occupied. Components other than crystals, such as inductors, capacitors, resistors or tuned circuits could be mounted on the strip. Such components could, for example, be mounted in cans and provided with contacts which mechanically engage fixed contacts, as in the crystal turret assembly.

In a further embodiment of the invention the turret could include assemblies which comprise a disc on a surface of which a number of components are printed radially by using normal printed circuit techniques. The components would be switched by rotating the disc relative to a fixed contact which bears against a rotary contact on the disc, and the complete arrangement would be housed within the knob used to rotate the disc.

In cases where a variation in the length of the leads associated with the switched circuit elements can be tolerated, it would be possible to keep the switched elements stationary and perform the switching operation by means of rotary switch contacts. The crystals could, for example, be mounted as in the embodiment of the invention which has been described, and two rotary contacts could be made to connect with the contacts of the selected crystals by rotation of the tuning knob.

It is to be understood that the foregoing description of specific examples of this invention is not to be considered as a limitation on its scope.

What we claim is:

1. Radio equipment comprising:

a rotatable knob having a hollow interior;

a pair of fixed contacts extending into said hollow interior parallel to the rotational axis thereof;

a plurality of circuit elements secured within said hollow interior and disposed radially with respect to said axis, each of said elements including a pair of switch contacts for selected engagement with said fixed contacts upon rotation of said knob;

a strip of material having a shape forming at least a portion of the surface of a cylinder coaxial with said axis;

said circuit elements being mounted on the concave surface of said strip with said switch contacts extending through said strip beyond the convex surface thereof; and

a plurality of containers each enclosing one of said circuit elements, each of said containers having a cross section in the plane of a cross section through said cylinder tapered from said concave surface of said strip toward said axis.

2. Radio equipment according to claim 1, wherein said elements are tuning elements.

3. Radio equipment according to claim 2, wherein said tuning elements are piezoelectric crystals.

4. Radio equipment according to claim 1, wherein said strip is a resilient plastic strip.

5. Radio equipment according to claim 1, wherein said strip is a resilient plastic strip; and

said elements are piezoelectric crystals.

References Cited by the Examiner UNITED STATES PATENTS 1,639,817 8/1927 Taylor 310-9 1,654,189 12/1927 Powell 310-9 1,663,682 3/1928 Crossley et a1. 310-9 2,078,909 4/1937 Gunther 334-51 2,141,563 2/1938 Skojic 200-125 X 2,157,576 5/1939 Schneider 310-9 2,183,723 12/1939 Pashke 334- 2,688,062 4/1953 Edman 200- 2,898,563 8/1959 De Cola 334-50 FOREIGN PATENTS 493,102 9/ 1938 Great Britain.

MILTON O. HIRSHFIELD, Primary Examiner.

HERMAN KARL SAALBACH, Examiner.

R. F. HUNT, J. D. MILLER, Assistant Examiners. 

1. RADIO EQUIPMENT COMPRISING: A ROTATABLE KNOB HAVING A HOLLOW INTERIOR; A PAIR OF FIXED CONTACTS EXTENDING INTO SAID HOLLOW INTERIOR PARALLEL TO THE ROTATIONAL AXIS THEREOF; A PLURALITY OF CIRCUIT ELEMENTS SECURED WITHIN SAID HOLLOW INTERIOR AND DISPOSED RADIALLY WITH RESPECT TO SAID AXIS, EACH OF SAID ELEMENTS INCLUDING A PAIR OF SWITCH CONTACTS FOR SELECTED ENGAGEMENT WITH SAID FIXED CONTACTS UPON ROTATION OF SAID KNOB; A STRIP OF MATERIAL HAVING A SHAPE FORMING AT LEAST A PORTION OF THE SURFACE OF A CYLINDER COAXIAL WITH SAID AXIS; SAID CIRCUIT ELEMENTS BEING MOUNTED ON THE CONCAVE SURFACE OF SAID STRIP WITH SAID SWITCH CONTACTS EXTENDING THROUGH SAID STRIP BEYOND THE CONVEX SURFACE THEREOF; AND A PLURALITY OF CONTAINERS EACH ENCLOSING ONE OF SAID CIRCUIT ELEMENTS, EACH OF SAID CONTAINERS HAVING A CROSS SECTION IN THE PLANE OF A CROSS SECTION THROUGH SAID CYLINDER TAPERED FROM SAID CONCAVE SURFACE OF SAID STRIP TOWARD SAID AXIS. 